Efficiency of hyperbaric oxygen therapy in experimental acute acoustic trauma from firearms

In acute acoustic trauma (AAT), excessive noise exposure causes rupture of cell membranes and decreased cochlear blood few. This leads to decreased ox ygen tension in inner ear fluids and reduction of a variety of different ox ygen-dependent cellular activities. Hyperbaric oxygen treatment (HBO) may h elp the cells suffering from hypoxia to survive. We exposed male Wistar rat s to 60 impulses of 162-dB SPL from a 7.62-mm assault rifle equipped with a blank adaptor. After the exposure. 15 animals were given HBO treatment For 90 min daily for 10 consecutive days at 0.25 MPa. After a survival time of 4 weeks, auditory brainstem responses were measured and the left cochleae processed for light microscopy. The impulse noise caused permanent damage t o the cochlea of all animals, with the most severe lesions in the lower mid dle coil, where a significantly smaller number of hair cells was missing in the HBO-treated group. The morphological damage was also reflected in func tion, as measured by auditory brainstem responses, which showed the greates t threshold shifts at 6.0. 8.0 and 10.0 kHz.